1. Field of the Invention
The present invention relates to a push button and, more particularly, to a push button having an illumination structure which can illuminate its outer periphery.
2. Description of the Related Art
Conventionally, an electrophotographic image forming apparatus such as a digital copying machine is known well in which the photosensitive layer of a uniformly charged photosensitive drum is exposed by being illuminated with light to form a latent image. Toner is attached to the photosensitive layer having the latent image to develop the latent image. The latent image is transferred to a sheet to form an image.
Conventionally, a push button is employed often to allow the user to instruct various operations to various types of apparatuses. For example, in an image forming apparatus such as a digital copying machine, a push button can be employed as a copy button which instructs execution of copying operation.
Such a push button sometimes has an illumination structure which illuminates the button from below to indicate whether or not the push button is in an active state, to make the push button stand out, or to improve the appearance.
For example, a button illumination structure described in Japanese Unexamined Patent Publication No. 2001-307595 (patent reference 1) comprises a hollow button with an upper portion made of a light-transmitting material. A light-emitting diode is provided under the button. Light emitted from below the button is transmitted through the upper portion of the button so that the user can recognize the light.
When the push button is illuminated from below so the user recognizes light emission of the push button, assume that the push button has a structure such as the illumination structure of the button of the patent reference 1. When the upper portion of the button and the light source are set close to each other to make a low-profile button component, the light source illuminates only the central portion of the button. In case that light emission is to be obtained around the button, the outer periphery of the button cannot be illuminated efficiently.
If the upper portion of the button and the light source are spaced apart from each other so the light diffuses to illuminate the outer periphery of the button as well, a low-profile button component cannot be obtained. As the upper portion of the button and the light source are spaced apart from each other, light emission to the user results in low illuminance.